Those white, fuzzy patches are almost always mold or mildew feeding on moisture, dirt, and skin oils left on the leather before storage. Winter closets, basements, and sealed boxes trap humidity, turning your shoes into a private greenhouse for fungi. While the sight is alarming, it doesn’t always mean the shoes are lost — but it does mean you need to act thoughtfully, not just wipe and wear.

Take moldy leather outside, brush off loose growth, then gently clean with a 50/50 mix of white vinegar and water, allowing the shoes to dry slowly before conditioning the leather. Avoid bleach and harsh chemicals that can burn color and weaken fibers. If the mold is deep, widespread, or the shoes are valuable, a professional leather cleaner is the safest option. Going forward, dry shoes completely, use breathable storage, desiccant packets, and occasional inspections to keep mold from ever taking hold again.